In vending and money changing machines, the handling of paper money is a problem due to the fact that the bills are often wrinkled, may have folded corners or edges, or even be torn. Some systems in use carry the bill through restricted tracks or paths, with multiple choice routes depending on the transaction. Damaged or folded bills tend to jam or hang up at various points, requiring frequent servicing of the machine. For prolonged service with a minimum of attention, it is necessary for the machine to handle bills with a variety of imperfections, without jamming or malfunctioning.